Soil physical environment as affected by double zero ... · the double zero tillage which further needs to be tested under different agro-climatic conditions under texturally divergent

An Asian Journal of Soil Science Volume 10 | Issue 1 | June, 2015 | 166-172 | e ISSN–0976–7231 Visit us : www.researchjournal.co.in

Soil physical environment as affected by doublezero tillage in rice-wheat cropping system ofnorth-west India

RAJAN BHATT AND S.S. KUKAL

HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE

MEMBERS OF RESEARCH FORUM:

Received : 24.03.2015; Accepted : 29.05.2015

SummaryHighly productive rice (Oryza sativa L.) and wheat (Triticum aestivum L.) cropping systemsare crucial for millions of rural and urbans in the Indo-Gangetic Plains (IGP) of south Asia. Thisintensive RWCS resulted in declining under groundwater table and degrading soil health. Anumber of resource conservation technologies are being propagated in the region to upliftdeclining water productivity and soil health. Among different propagated resource conservationtechnologies-double zero tillage (ZT-wheat) in both crops found to be adopted in the region ata large scale which lessens cost of cultivation with no-field preparation and no-pre-sowingirrigation factor. Further, as wheat sown in loose and anchored rice straw thus, emit burning ofrice residues and finally, reduces air pollution and improves “blank gold” status (Soil organiccarbon). Zero tillage supposed to improve the declining soil physical properties; crop andwater productivity thought visible effects appeared after 4-5 years of adoption. The treatmentincluded two tillage levels viz., conventional and zero tillage and three rice tillage viz., puddle,conventionally and zero tilled with two establishment methods viz., direct seeded rice (DSR)and mechanically transplanted rice (MTR). Objective of the present study was to delineate theeffect of double zero tillage from 2012-2014 on the soil physical environment and findingssuggests that double tillage was not able to significantly effect of the physical properties ofthe soil as adaptation of CA based component technologies evolved over the time. Thus, bestbenefits of double zero tillage might be significant after 3-5 years of continuous adoption ofthe double zero tillage which further needs to be tested under different agro-climatic conditionsunder texturally divergent soils.Key words : Double zero tillage, Rice-wheat cropping system, Physical environment, North-west India

How to cite this article : Bhatt, Rajan and Kukal, S.S. (2015). Soil physical environment as affected bydouble zero tillage in rice-wheat cropping system of north-west India. Asian J. Soil Sci., 10(1) : 166-172.

A Case Study

Corresponding author :RAJAN BHATT, Department of SoilScience, Punjab AgriculturalUniversity, LUDHIANA (PUNJAB)INDIA

IntroductionRice–wheat cropping system (RWCS) is the most

important cropping system for food security in south Asia(13.5 M ha), providing food for more than 400 million

people (Ladha et al., 2003) but led to decline ofunderground soil water and deterioration of the soil health(Hira et al., 2004; Kukal et al., 2014) in the region.Conventionally, rice is established in puddle soils withheavy water and labour inputs (Dawe, 2005), causes

DOI : 10.15740/HAS/AJSS/10.1/166-172

Co-authors :S.S. KUKAL, Department of SoilScience, Punjab AgriculturalUniversity, LUDHIANA (PUNJAB)INDIA

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167HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE Asian J. Soil Sci., (June, 2015) 10 (1) :

sub-surface compaction because of repeated puddlingsof coarse and medium textured soils (Sur et al., 1981;Kukal and Aggarwal, 2003a) restricts the root growth ofwheat in addition to creating aeration stress (Kukal andAggarwal, 2003b). Puddling deteriorated soil physicalproperties by breaking down soil aggregates, inducedchanges in pore size distribution; the cone indexdecreased after puddling and gained strength during thesubsidence stage of the puddle soil, and the bulk densityof soil increased and hydraulic conductivity decreased30 and 60 days after puddling.

Generally farmers burnt the paddy residues at theirfield for timely sowing of wheat seeds during Rabi seasonwhich cause loss of huge nutrients as about 40 per centof the N, 30-35 per cent of the P, 80-85 per cent of theK, and 40-50 per cent of the S absorbed by rice remainsin the vegetative parts at maturity (Dobermann andFairhurst, 2000) which lost on burning which ultimatelydetonating the soil physico-chemical health.

To address these challenges of RWCS, conservationagriculture (CA) based alternative tillage and cropestablishment methods viz., ZTW-DSRZT have beendesigned and tested in IGP (Malik et al., 2014 and Jat etal., 2013). The conservation agriculture (CA) involvesa paradigm shift from intensive tillage to zero or reducedtillage, establishment of permanent organic soil cover witheconomically viable crop rotation that complementreduced tillage and residue retention. Change in the soilphysical properties as affected by the double zero tillage(ZTW-DSRZT) had a profound effect on the productivity,profitability and sustainability of the rice-wheat croppingsystem (Bhaduri and Purakayastha, 2014 and Dikgwatlheet al., 2014). However, the magnitude of benefits of CAbased technologies tends to be site and situation specificand cannot be overly generalized across farming systems(Hobbs, 2007) and realized after 2–3 years as theadaptation of CA based component technologies evolvedover the time (Jat et al., 2014).

Generally zero tillage adopted only during wheatseason but to get the full benefits of ZT, both rice andwheat need to be grown with a ‘double zero-tillage’system (Jat et al., 2006b and Bhushan et al., 2007).However, few studies present in literature showing theeffect of double zero tillage in the RWCS on the physicalenvironment and still doubts are there as within two years,some studies showed the significant improvement.Keeping this objective in view, present investigation wasmade to evaluate the impact of double zero till (ZTW-

DSRZT) practised for two years on the different soilphysical properties as compared to the conventionalmethods (CTW-DSRP).

Resource and Research MethodsSite description :

The field experiments were carried out at theresearch farm (30°54’N, 75°98’E, 247 m above sea level)of Punjab Agricultural University, Ludhiana, India, during2012-14. The experimental soil was sandy loam (sand65-68 %, clay 11-3%), neutral to slightly alkaline, non-saline and medium in soil organic carbon (0.44%) in thesurface layer (Table 1). The soil had sub-surface compactlayer (bulk density of 1.74 Mg m-3 at 15-30 cm). Theavailable nutrients were in the medium range whilemoisture content (%, g g-1) on an average decreased to71.5 per cent from field capacity to permanent wiltingpoint. The depth to the ground water at the site wasaround 24 m and the quality of water was good for allcrops (Table 2). The experimental site was under puddletransplanted rice for the last 20 years except that thefield was under direct dry-seeded rice (DSR-CT) sownunder tilled conditions during the immediate previous year(2012). The climate is subtropical with hot and drysummers (March-June), wet monsoon season (late Juneto mid-September) and a cool dry winter (October-February). The long-term average annual rainfall is 734mm, 85 per cent of which occurs during a short periodof July-September.

Treatments and experimental design :The treatments consisted of zero- (direct-drilling of

wheat in standing stubbles of the previous crop, ZTW)and conventional-tillage (disked twice followed by 2passes of tractor-drawn cultivator and one planking,CTW) for wheat in main plots (13.8 m × 25.1 m) withthree replications. In the following rice crop, the mainplots were splited into two sub-plots for differential riceestablishment viz., direct-seeded rice (DSR) andmechanically transplanted rice (MTR). These subplotswere further splited into three sub-sub plots of 49.7 m2

(13.8 m × 3.6 m) for differential tillage treatments inrice viz., puddle (P), dry and (CT) and zero-till (ZT).The tillage treatments in rice were randomly allocatedin subplots of both DSR and MTR. During wheat season,rice straw load of 4.4 t ha-1 retained on ZTW plots whileduring rice season all the straw load was removed. Asper objective of present investigation, initial soil physical


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HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE 168 Asian J. Soil Sci., (June, 2015) 10 (1) :

properties analyzed before onset of the experiment andthen after practising double zero till for two years samephysical properties analysed again to delineate anysignificant change.

Measurement of different physical properties :Bulk density was determined by using the core

sampler method (Bodman, 1942). In situ bulk densitywas calculated after obtaining undisturbed soil samplesin metallic cores having internal diameter of 5.3cm anddepth of 5.0cm from different soil depths [Fig. A(d)].The fresh weight of soil samples was recorded. The soilfill cores were oven-dried at 105 °C for 24 hours andwere weighted to record dry weight of the samples. Thebulk density was then calculated as the ratio of dry weightof soil samples to the internal volume of the metallic core.

The infiltration rate of field was determined usinginfiltrometer method [Fig. A(a)] (Herman, 1986) whilefor the particle size distribution for delineating the texturalclass of the soil was calculated using international pipettemethod (Piper, 1966) while organic carbon (%) estimatedby Walkley and Black’s rapid titration method (1934).

The moisture content at the field capacity and permanentwilting point in different layers of the soil profile wasdetermined by Pressure plate apparatus [Fig. A(b)](Richard and Weaver, 1943).

The aggregate size distribution was determined usingwet sieving technique (Yoder, 1936). To representaggregation status of soil mean weight diameter wascalculated as follow :

n

1ii

n

1iii

W

Wd MWD

where, di is the mean weight diameter of each sizefraction in mm, n is the number of size fractions and Wiis the weight of aggregates in the corresponding sizefractions. Saturated (using guleph permeameter) andunsaturated (using disk permeameter) hydraulicconductivities throughout the soil profile was calculatedusing the disk permeameter [Fig. A(c)].

Research Findings and DiscussionEfforts were made to evaluate the impact of double

a

dc

b

Fig. A : Measurement of different physical properties of the soil viz., infiltration rate (a), hydraulic properties (b), Hydraulicconductivity and bulk density

SOIL PHYSICAL ENVIRONMENT AS AFFECTED BY DOUBLE ZERO TILLAGE IN RICE-WHEAT CROPPING SYSTEM

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zero till (ZTW-DSRZT) on the different soil physicalproperties viz., bulk density, hydraulic conductivity,hydraulic properties (Moisture % w/w at FC and PWP),infiltration and aggregation. Following discussion coversthe impact of double zero till technologies on the soilphysical environment.

Bulk density (mg m-3) :In the present investigation of two years (2012-

14), no significant effect of double zero till wasobserved on the bulk density throughout the soil profileupto 150 cm (Table 1) though surface soil (0-15 cm)showed some increments. However, contrary to ourstudy Jat et al. (2009) reported that double zero till(ZTDSR-ZTW) had significantly higher bulk densityin the 0–5 and 5–10-cm soil profile than with othert illage sys tems, whereas it was higher underconventional-tillage (PTR-CTW and CTDSR-CTW)

in the 10–15 and 15–20-cm soil layers compared withZTDSR-ZTW. Published studies revealed thatpuddling induced high bulk density in subsurface layers(15–30 cm) in rice based systems (Sharma and DeDatta, 1985; Hobbs and Gupta, 2000).

Hydraulic properties (Moisture content % w/w atFC and PWP) :

The hydraulic properties throughout the soil profile(upto 150 cm) was not significantly improved ascompared to the plots under conventional system (CTW-DSRP) (Table 1) and shorter time period might be onereason for that as the positive effect of conservationtechnologies realized after 2-3 years as the adaptationof CA based component technologies evolved over thetime (Jat et al., 2014). The moisture content almostreduced to half as the studied scenario shifted from FCto PWP.

Table 1 : Physical properties as affected by double zero till scenario

Bulk density (Mg m-3) Moisture content (% w/w) at 0.3 bar (FC)

Moisture content (% w/w) at 15 bar (PWP)

Soil texture Sand %, (Clay %) Organic carbon (%)

Soil depths Initial ZTW-DSRZT Initial ZTW-

DSRZT Initial ZTW- DSRZT Initial ZTW-

DSRZT Initial ZTW-DSRZT

0-15 1.66 1.68 11.3 11.4 7.7 7.8 64.7, (11.3) 64.8, (11.2) 0.45 0.47 15-30 1.74 1.73 10.4 10.5 6.2 6.1 65.9, (11.3) 66.0, (11.5) 0.42 0.43 30-60 1.59 1.59 12.1 12.1 6.4 6.3 66.8, (12.6) 66.6, (12.7) 0.35 0.36 60-90 1.63 1.62 11.3 11.4 6.7 6.7 67.6, (12.7) 68.0, (12.8) 0.37 0.36 90-120 1.57 1.58 12.1 12.0 7.3 7.4 68.2, (12.3) 68.4, (12.5) 0.34 0.35 120-150 1.61 1.60 12.5 12.6 6.6 6.6 68.8, (11.9) 68.9, (12.0) 0.32 0.32


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Fig. 1 : Effect of double zero till plots on the infiltration rate (a) and cumulative infiltration (b) as compared to the conventionals ys te m

Cumulative time (minutes)

Infil

tratio

n ra

te (

cm h

r-1)

Initial ZTWDSRZT25

20

15

10

5

00 20 40 60

Initial ZTWDSRZT

Cumulative time (minutes)

Cum

ulat

ive

infil

tratio

n (c

m)

14

12

10

8

6

4

2

00 20 40 60

(a) (b)


Organic carbon (%) :Organic carbon throughout the soil profile remained

almost same and was not significantly affected by thedouble zero tillage of the wheat rice cropping systempractised for the four seasons (Table 1) which might bebecause of retention of straw loads of 4.4 t ha-1 duringwheat only. Further, it was observed that organic carbondecreased down the profile and after 30 cm almost nochange observed in the double zero tilled plots ascompared to the conventionally tilled plots viz., CTW-DSRCT plots.

Soil texture :Double zero tillage technology in RWCS was not

able to influence the soil texture at all after two years asper cent sand and clay remained almost same through-out the soil profile as it was before conduction of theexperiment indicating that soil texture not influenced bydouble zero tillage (Table 1).

Infiltration :Infiltration is the capacity of the soil with which it

allowed the water to enter and the movement of thewetting front depends upon several pre-condition astexture of underlying soil, moisture content of the soilprofile and it is an indicator of the soil health. At the endof our experiment, no significant improvement in theinfiltration rate and cumulative infiltration was observedunder the double zero till plots as compared to theconventional system (CTW-DSRP) (Fig. 1 a and b).However, slight improvement in the cumulative infiltrationrate was observed in the double till plots. Jat et al. (2009)also reported the similar infiltration rates in double zerotill plots than the plots which were under CTW-PTR.

Hydraulic conductivity :Hydraulic conductivity (cm s-1) is an important soil

physical property and indicated the water intakeconduction behaviour of the soil. During the current

investigation hydraulic conductivities (both saturated andun-saturated) of the sandy loam soil reported to havenon-significant effect by the double zero till viz., ZTW-DSRZT during the last four cropping seasons and it’srange remained almost similar to that in the conventionalsystem of rice-wheat establishment (Fig. 2).


Fig. 2 : Saturated and unsaturated hydraulic conductivity asaffected by conventional and conservation tillage sys-tems over the last four seasons

Saturated Unsaturated Saturated Unsaturated

Initial hydraulic conductivity

After four zero till seasons

Hyd

raul

ic c

ondu

ctiv

ity(c

m se

c-1)

0.80.70.60.50.40.3020.1

0

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Table 2: Per cent soil aggregates initially and doubles ZT plots from last four seasons Per cent soil aggregates Sieve size (mm) Initial status ZTW-DSRZT

>2.0 61.92 61.96 1.0 2.80 2.78 0.5 1.65 1.64 0.25 8.98 8.96 0.10 4.62 4.60 <0.10 20.09 20.06

Aggregation/mean weight diameter :The primary soil particles (sand, silt and clay) tend

to cohere to form secondary particle called aggregate.The size distribution of aggregates in soils indicatesretention of water as their size is important in determiningthe dimensions of pore space in cultivated soils.

It was revealed that the mean weight diameter andpercentage of weight retained in each size fractionremained almost similar and non-significant effect wasobserved in plots under conventional tillage and underconservation tillage (ZTW-DSRZT) from the last fourseasons (Table 2 and Fig. 3).

Contrary to result of present study, Jat et al. (2009)double no-till (ZTDSR-ZTW) had significantly higher soilaggregates (>0.25 mm) than conventional-tillage (PTR-CTW) which might be because of their retained strawload during both the seasons on to the soil surface indouble ZT plots while in our study straw load of 44 tha-1 retained only during the wheat season. Further, underconventional-tillage, soil aggregation was static acrossthe seasons, whereas it improved over time under double


no-till and permanent beds. The mean weight diameterof aggregates (average of all size groups) wassignificantly higher under ZTDSR-ZTW and increasedover time compared with conventional-tillage (CTW-PTR).

Conclusion :Double zero tillage viz., ZTW-DSRZT from

wheat 2012-13 to rice 2014 observed to have non-significant effect on the improvement of the differentsoil physical properties from the initial values. Thismight be because of the reason that conservationagriculture technologies components including doublezero tillage evolved over the time. However, after 3-5 years onwards, double zero tillage (ZTW-DSRZT)had a profound improvement in the soil physicalenvironment and thus, favourably effect on theproductivity, profitability and sustainability of the rice-wheat cropping system. The soil physical propertiesin terms of soil aggregation, steady-state infiltrationrate and compaction does not significantly improvedunder the double zero-tillage system compared withconventional RWCS. Further evaluation of double zerotillage in RWCS need to be re-evaluated after 5 yearsand afterwards, double zero tillage may improve thesoil physical environment significantly. Furtherevaluation of double zero tillage viz., ZTW-DSRZTin RWCS is recommended at different agro-climaticconditions under texturally divergent soils for morethan 3-5 years to have significant improvement in thesoil physical environment.

Acknowledgment :Authors are extremely thankful to Department of

Soil Science, Punjab Agricultural University, Ludhiana,India, for providing necessary facilities to carry out thisstudy.

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Fig. 3 : Mean weight diameter as affected by four season zerotill plots

Unsaturated After four seasons zero till

Mea

n w

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t dia

met

er

2.5

2

1.5

1

0.5

0

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Soil physical environment as affected by double zero ... · the double zero tillage which further needs to be tested under different agro-climatic conditions under texturally divergent